1. Field of the Invention
This invention relates to a steering lock apparatus that locks a steering shaft and hence a steering wheel with a key rotor of a key cylinder rotated to a lock position.
2. Background
In a steering lock apparatus for motor vehicles in general, the rotation of the steering shaft and hence the steering wheel can be locked by rotating the key rotor of the key cylinder to the "LOCK" position, which is a locking position, with a key and by engaging a lock bar with the steering shaft side when the key is taken out of the key rotor.
When the key is inserted into the key rotor and the key rotor is then rotated to the operating positions ("ACC", "ON", "START" positions), a cam projection of the cam shaft that integrally rotates with the key rotor moves the lock bar to disengage the lock bar from the steering shaft side, so that the steering shaft and hence the steering wheel can be unlocked. Further, as the cam shaft rotates, an ignition switch is also operated.
Therefore, the steering lock apparatus of this type is an effective burglarproof device, because the steering lock apparatus can not operate the steering wheel and the ignition switch when there is not the key.
However, in such steering lock apparatus, when the key cylinder is caused to come off the body by some device or as a result of the front portion of the body having been broken with the steering shaft having been locked, the cam shaft is exposed within the body, and this condition leaves the cam shaft rotatable.
To overcome this problem, the inventors filed Japanese Utility Model Application No. Hei. 3-51917 (Unexamined Japanese Utility Model Publication No. Hei. 4-134773).
The apparatus disclosed in the aforementioned utility model publication is characterized not only as arranging an engagement body having an engagement groove so as to rotate integrally with the cam shaft, but also as arranging a block member in the body so as to be movable between an engagement position and a disengagement position, and further as arranging a regulating member that engages with the block member when the block member moves to the engagement position.
In this apparatus, the block member is held in the disengagement position while biased by the key cylinder under the normal condition in which the key cylinder is accommodated in the body. When the key cylinder is caused to come off the body by some device with the steering shaft having been locked, the block member moves to the engagement position by an urging force of an urging device to engage with the engagement groove of the engagement body. As a result of such engagement of the block member, the rotation of the engagement body and hence the cam shaft can be blocked.